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    <title>Document</title>
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    <script>
        var a=(b=1,c=2,d=3);  //b=1,c=2,d3,a=3
        function foo(){
            return a++,++b,a+b;  //a=4,b=2,a+b=6
        }
        console.log(foo());  //6
    </script>
</body>
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